In a conventional communications receiver, there are two conflicting requirements: high sensitivity and high linearity. High sensitivity refers to the receiver characteristic of a low noise figure with high gain so that the receiver is sensitive to a weak signal. A low noise figure LNA provides better sensitivity to the receiver and good SNR for a weak signal. However, a low noise figure LNA with high gain fails to provide adequate SNR in the presence of strong interference (i.e., jammer) because the intermodulation level increases. The intermodulation level increase is due to the low third order intercept point (IP3) and low 1 dB compression point (P1dB) for a high sensitivity receiver.
High linearity refers to the receiver characteristic of a high third order intercept point (IP3) and a high 1 dB compression point (P1dB). A high linearity receiver has improved immunity against strong signals and against strong interferences (i.e., jammers). That is, a high linearity receiver has less distortion (e.g., intermodulation product levels, gain compression, phase non-linearity, AM-PM conversions, etc.) in the presence of strong signals or strong interferences than a high sensitivity receiver. However, a high linearity receiver (i.e., the LNA) has a higher noise figure and lower gain and therefore cannot provide optimal sensitivity and SNR in the presence of a weak jammer or if no jammer appears at all. In a particular input signal environment, to determine the appropriate characteristic of the receiver (high sensitivity versus high linearity) that is needed, a jammer detector coupled to the receiver is used. The jammer detector detects the presence of jammers. Conventional jammer detectors are typically optimized for narrowband, single band operation and do not provide both wideband and narrowband jammer detection for a multiband, multi-standard receiver over a broad frequency range.